What can a percentage calculator do?
Percentages show up everywhere: exam marks, discounts, tip math, price changes, and “what percent of the assignment did I finish?” This tool covers the four patterns people search for most — without uploading the numbers to a cloud form.
X% of Y
Multiply the value by the rate as a decimal. Fifteen percent of 80 is 12. Useful for discounts, tax estimates (educational only), and “how many points is this category worth?”
Marks as a percentage
Scored 45 out of 60? That is 75%. Enter part and whole in “X is what % of Y?” mode. For a weighted final that still sits ahead of you, switch to the Final Grade Calculator— plain mark % and weighted course grade are different questions.
Percent change
Going from 50 to 65 is a 30% increase relative to the start. Always divide by the old value. If the starting value is zero, percent change is undefined — the tool tells you instead of inventing a number.
Increase or decrease by a percent
Apply +10% or −10% to a quantity when you already know the rate. Example: 200 increased by 10% → 220. Decrease flips the sign in the same formula.
Privacy
Grades, prices, and practice numbers stay in your browser after the page loads. Airplane mode still works. This page does arithmetic only — not financial, tax, or academic advice.